simply make small talk and buy a print/or about to take a pic with her. when you're about to pay/tip (to her, not the beta orbiter that is handling her mech) pull out your money clip (this is important: don't be a fat/dirty beta. at least clean up, dress nice and smell nice). but make sure you have over 600 (100's and 20's). pull out a five or 3 ones (if you're tipping).
tell her thanks and be on your way.
about 30 min later walk by and make sure you both see each other and smile.
hour later do the same (if she doesn't stop or wave you to come to her, then she's not one of those girls)
but if she does, she will ask what you're doing later and she'll start talking about how later she's doing a photoshoot. this is the time to ask or let her tell you how much she's being 'paid'. go from there (unless you're full of spaghetti)